1. Field of the Invention
This invention relates to cooling towers and more particularly to drift eliminators utilized downstream of the evaporative portion of such cooling towers.
2. Description of the Prior Art
Nuclear power plants have spawned emphasis upon environmental disturbances known as thermal pollution. Thermal pollution is the term utilized to designate the effect of the discharge of large quantities of condenser coolant water typically 200,000 gallons per minute, into the environment adjacent a power plant. This effluent water is usually 20.degree. to 25.degree.F higher than the temperature of the influent water. The affect of this temperature rise and thermal gradient upon the marine and aquatic life is the subject of much concern.
To reduce the amount of thermal pollution cooling towers are often utilized and while the use of cooling towers offers some relief for thermal pollution, they introduce other adverse environmental effects. Cooling towers produce drift, which is formed by tiny water droplets 50-10.mu. in size entrained in the effluent air and a plume which includes the drift but is mainly condensation which forms droplets 10-20.mu. in size. The droplets are formed by cooling the moisture laden air resulting from the evaporative mechanism of the tower. The environmental impact of the plume has many facets which range from the aesthetically unappealing plumes to the formation of localized fog and ice which produce local hazardous driving conditions. Drift droplets, since they are larger, can cause "rain" downstream of the cooling tower and icing conditions in the winter. If the cooling tower water is of high mineral content soil contamination may result.
The reduction and elimination of drift from a cooling tower and its associated affects have been subject of considerable research. Devices known as drift eliminators have been designed with varying degrees of success.
Wet or wet-dry cooling towers utilize sprays and packing to break the water into small droplets to increase surface area so as to bring the water into intimate contact with influent cooling air, thus many of the droplets become airborne and flow with the cooling air. To remove these airborne or entrained droplets from the effluent air, drift eliminators are generally disposed downstream of the evaporative cooling portion of the towers and generally comprise a plurality of closely disposed parallel chevron or sinusoidal louvers or vanes. The spaces between the vanes form passageways which cause the effluent air to make frequent changes in direction. These drift eliminators utilized the inertial effect of the multiple turns to cause the droplets to impinge upon the louvers and coalesce covering the surface thereof, and then flow by gravity therefrom. These drift eliminators are affective as they remove a substantial amount of entrained moisture from the effluent air, however, they produce large pressure drops.